An airbag cover of an automobile airbag system is required to have rigidity suitable for applications such as a driver's seat or a passenger seat, to have high tensile elongation at break so that the airbag cover does not split other than in a tear line section (a thin section of the airbag cover provided so as to make the airbag cover split when the airbag is deployed), to have high impact strength at low temperature so as to withstand use in a cold district, to have an appearance appropriate for an interior component of an automobile, etc.
As such an airbag cover, many injection-molded bodies formed using a polyolefin-based thermoplastic elastomer composition that contains a propylene-based resin and an ethylene-propylene-non-conjugated diene copolymer rubber have been proposed. For example, JP•A•8-27331 proposes an injection-molded body formed using a thermoplastic elastomer composition that contains a propylene-ethylene random copolymer, an ethylene-propylene-non-conjugated diene copolymer rubber, and a low-density polyethylene. JP•A•2000-72937 proposes an injection-molded body formed using a thermoplastic elastomer composition that contains a propylene-ethylene copolymer, a propylene-1-butene random copolymer, and two types of ethylene-propylene-5-ethylidene-2-norbornene copolymer rubbers. Furthermore, JP•A•2008-45037 proposes an injection-molded body formed using a thermoplastic elastomer composition that contains a propylene-based resin produced by multistage polymerization and an ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber.